During the past several decades, the hippocampus has been an empirical focus of age-related memory decline. While this is justified, the extent to which changes in the perirhinal cortex, a region extensively interconnected with the hippocampus, contribute to age-related behavioral deficits is unknown. Humans with lesions of the hippocampus lose the ability to form new memories while humans with lesions of the perirhinal cortex develop semantic dementia, a condition characterized by an insidious and gradual breakdown in semantic knowledge. Thus, while the hippocampus is critical for forming new memories, the perirhinal cortex may be integrally involved in providing content to those memories. Whether the response properties of perirhinal neurons change, and/or there is a decline in perirhinal plasticity during normal aging that contributes to memory impairment, is the major question addressed in the present proposal. To begin to address this, perirhinal function and the mechanisms of recognition memory will be investigated in adult and aged rats using electrophysiological recordings and imaging neural ensembles with cellular compartmental analysis of temporal activity by fluorescence in situ hybridization [unreadable] [unreadable]